Quantitative high-pressure liquid chromatographic procedure for the determination of plasma and tissue levels of 2,4-diamino-5-(3,4-dichlorophenyl)-6-methylpyrimidine (metoprine) and its application to the measurement of brain capillary permeability coefficients.

A high-pressure liquid chromatographic assay for metoprine levels in aqueous media, serum, and tissue extracts has been developed that can measure concentrations of the drug in the 25-100 ng range with accuracy, reproducibility, and ease. The half-time for metoprine disappearance from rat plasma and capillary permeability coefficients for metroprine in rate brain tissue determined with this method are in excellent agreement with values determined for related drugs using labeled compounds.